The invention relates to an electronic power module including at least one power module disposed on an electrically insulating substrate, and to a semi-conductor power component designed to equip such a substrate. The electronic power module of the invention is particularly intended to be used for mounting insulated grid bipolar transistors (IGBTS) in power distribution circuits of the railway industry.
It is known that the performance of electronic power modules is limited by the temperature reached by the electronic power components in operation. For example, beyond 150xc2x0 C., the performance of a silicon chip is significantly degraded. As a result, it is very important to evacuate effectively the heat dissipated by the Joule effect, so as to maintain an optimum operating temperature in the components, and thus be able to increase the usable power or the reliability of the system.
In general, electronic power modules designed for railway traction are constituted by a power component soldered onto a substrate comprising an electrically insulating wafer made of aluminum nitrate AlN that is covered on its bottom and top faces by copper metallization using a method known as direct bonding copper (DBC), the substrate being cooled by a radiator in contact with the bottom layer of copper. However, such electronic modules present the drawback of having bonding layers at the solders and the metallizations which constitute thermal barriers, considerably reducing capacity to transmit heat through the substrate, thereby limiting the dissipation of energy through the cooling radiator.
The object of the present invention is thus to propose an electronic power module which remedies those drawbacks while ensuring excellent cooling of the power components.
To this end, the invention provides an electronic power module including at least one semi-conductor power component disposed on an electrically insulating substrate, wherein the semi-conductor power component includes a face in contact with the substrate, which face is metallized in part and is covered in part in a diamond layer, the metallized portion being in contact with a conductor track provided on the surface of the substrate, and the diamond-covered portion being in register with an opening formed in the substrate, said substrate including a face remote from the semi-conductor component which is cooled by a liquid coolant, the liquid coolant flowing into the opening and over the surface of the diamond-covered portion.
In particular embodiments, the electronic power module can comprise one or more of the following characteristics taken in isolation, or in any technically feasible combination:
the face of the semi-conductor power component in contact with the substrate is metallized at its periphery and covered in a diamond layer over the rest of its surface;
the diamond layer is deposited on the semi-conductor power component by chemical vapor deposition (CVD);
the diamond layer covering the semi-conductor power component forms excess thickness which is inserted into the opening of the substrate, said opening having a shape that is complementary to the shape of the diamond layer;
the semi-conductor power component is an IGBT component; and
the substrate is made of aluminum nitrate AlN or aluminum.
The invention also provides a semi-conductor power component designed to equip such an electronic power module, the component including a face designed to contact a substrate, which face is metallized in part and is covered in part in a diamond layer.
According to another characteristic of the semi-conductor power component of the invention, the face is metallized at its periphery and covered in a diamond layer over the rest of its surface.